Oxime ligands for Pd catalysis of the Mizoroki–Heck reaction, Suzuki–Miyaura coupling & annulation reactions

Article abstract of DOI:10.1080/00397911.2020.1826969

Monodentate and bidentate chelating oximes are readily available ligands for the Pd catalysis of the Mizoroki–Heck reaction and the Suzuki coupling. High yields were obtained in the Suzuki coupling in aqueous dioxane with TBABr as additive. The oximes can be easily synthesized from the corresponding ketones or aldehydes and thus provide a very large number of nitrogen-based ligands. They have the advantage of not undergoing oxidative degradation, common for phosphine ligands. Chelating oximes with Pd(OAc)₂, activate aryl iodides to give high yields of the substitution products in the Mizoroki–Heck reactions as well as the Suzuki coupling. Acetophenone oxime ligand with Pd(OAc)₂, catalyzed the reaction of aryl iodides with 1,2-disubstituted alkenes in moderate to high yields. As a test example, the LaRock indole annulation and synthesis of isocoumarin were achieved with acetophenone oxime ligand and Pd(OAc)₂ in high yields.

Full text of DOI:10.1080/00397911.2020.1826969

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
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Oxime ligands for Pd catalysis of the
Mizoroki–Heck reaction, Suzuki–Miyaura coupling
& annulation reactions
Pronnoy G. Bangar , Pradip D. Nahide , Heena K. Meroliya , Shobha A.
Waghmode & Suresh Iyer
To cite this article: Pronnoy G. Bangar , Pradip D. Nahide , Heena K. Meroliya , Shobha
A. Waghmode & Suresh Iyer (2020): Oxime ligands for Pd catalysis of the Mizoroki–Heck
reaction, Suzuki–Miyaura coupling & annulation reactions, Synthetic Communications, DOI:
10.1080/00397911.2020.1826969
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SYNTHETIC COMMUNICATIONSV
https://doi.org/10.1080/00397911.2020.1826969
Oxime ligands for Pd catalysis of the Mizoroki–Heck
reaction, Suzuki–Miyaura coupling & annulation reactions
Pronnoy G. Bangara,b, Pradip D. Nahidea, Heena K. Meroliyac, Shobha A.
Waghmodec, and Suresh Iyera,b
b
aOrganic Chemistry Division, National Chemical Laboratory, Pune, India; Academy of Scientific and
c
Innovative Research (AcSIR), New Delhi, India; Abasaheb Garware College, Pune, India
ABSTRACT
ARTICLE HISTORY
Received 19 May 2020
Monodentate and bidentate chelating oximes are readily available
ligands for the Pd catalysis of the Mizoroki–Heck reaction and the
Suzuki coupling. High yields were obtained in the Suzuki coupling in
aqueous dioxane with TBABr as additive. The oximes can be easily
synthesized from the corresponding ketones or aldehydes and thus
provide a very large number of nitrogen-based ligands. They have
the advantage of not undergoing oxidative degradation, common
for phosphine ligands. Chelating oximes with Pd(OAc)2, activate aryl
iodides to give high yields of the substitution products in the
Mizoroki–Heck reactions as well as the Suzuki coupling.
Acetophenone oxime ligand with Pd(OAc)2, catalyzed the reaction of
aryl iodides with 1,2-disubstituted alkenes in moderate to high
yields. As a test example, the LaRock indole annulation and synthesis
of isocoumarin were achieved with acetophenone oxime ligand and
Pd(OAc)2 in high yields.
KEYWORDS
Isocoumarin; LaRock
annulation; Mizoroki–Heck
reaction; oximes;
Suzuki coupling
GRAPHICAL ABSTRACT
Introduction
Though nano catalysts are state of the art, the dynamic association, dissociation of
ligands conjures the magical wizardry associated with homogeneous catalysis. Thus, lig-
and-based homogeneous catalysis attributes activities and selectivities otherwise
unachievable through normal organic synthesis. While huge reactivity is attributed to
CONTACT Suresh Iyer
s.iyer@ncl.res.in
Organic Chemistry Division, National Chemical Laboratory, Dr. Homi
Bhabha Road, Pashan, Pune, Maharashtra, India
Supplemental data for this article can be accessed on the publisher’s website.
ß 2020 Taylor & Francis Group, LLC

2
P. G. BANGAR ET AL.
nano catalysts, ligand complexation ramps up homogeneous catalysis to even greater
heights of selectivity, reactivity and efficiency. Ligand complexation entwined with metal
co-ordination and oxidation states, enhances the homogeneous catalysis of organic
transformations. Ligand accelerated catalysis is a well-established phenomena exempli-
fied by the Sharpless dihydroxylation. Here, the life cycle of catalyst metal elements is
highly enhanced by co-ordination. Ligand architecture and engineering are a complex
arena of organometallic catalysis and a vast and fruitful exercise in organic synthesis.
Thus, by the virtue of their design and nature, ligands induce magical properties to
metal atoms in homogeneous catalysis. Phosphine ligands are a synthetic wizardry lead-
ing to vast complex structures which are though tedious synthesis in nature. Nitrogen
compounds are excellent alternatives for phosphine ligands, which have become ubiqui-
tous and synonymous with Pd and homogeneous catalysis, including industrial applica-
tions.[1] We and several other authors have earlier reported the use of easily obtainable
nitrogen ligands for the Mizoroki–Heck reaction, the Suzuki–Miyaura coupling and
other reactions.[2] Complexation of metals with oximes is well known and their ready
availability from the corresponding ketones and aldehydes by simple derivatization or
other methods make them very attractive.[3,4] Aromatic oximes due to their directed
ortho palladation lead to molecular marvels, palladacycles; which are exciting catalysts
as well as possessing other properties.[4] They provide competitive phosphine ligand
alternatives for the Mizoroki–Heck reaction, Suzuki–Miyaura and related cross-coupling
reactions.[5] Simpler complexes with mono or bidentate co-ordinating oximes are wait-
ing to be explored. Unlike phosphines, NHCs, SALEN, di-imines, cyclopentadienes, and
many other ligands, oximes are easy to synthesize and metal complexation simple to do
in the laboratory and little studied in organometallic catalysis for organic synthesis, like
cross-coupling reactions, though their ligating properties and co-ordination chemistry
are well known. Oximes possess strong coordinating property as well as facile dissoci-
ation for attenuation of metal reactivity. They are excellent coordinating groups for
various transition metals forming extremely stable metal complexes in very high
yields.[4] While ligands can be spectatorial, fruitful ligand intervention is an essential
feature of homogeneous catalysis, affecting stereo selectivities, activity, and efficiency.
The use of DMG, DAB, Salen, 8-HQ, Imines, Oxazolidines, nitrogen Pd cycles, and
several other N-based ligands gives high yields in the Mizoroki–Heck reaction and
Suzuki coupling.[6] PdCl2DMG showed promising activity for the Mizoroki–Heck reac-
tion of aryl iodides and some bromides.[2a] A novel 2-(diphenylphosphino)benzaldoxime
ligand has been used for the Suzuki coupling of aryl bromides.[7]
Phosphines have been shown to inhibit the Suzuki–Miyaura coupling of aryl halides,
thus limiting catalyst efficiency. Also, when using Pd(PPh3)4, significant incorporation
of phenyl groups from the PPh3 has been shown to occur. So ligand free, non-phos-
phine alternatives have been explored successfully and TBABr or PEG found to be an
excellent additive-solvents for high yielding reactions in aqueous media.[8] Bora and
coworkers have reported the use of oxime ethers as ligands in the aqueous phase Pd
catalysis of the Suzuki–Miyaura coupling. Their catalytic activity is based on the in situ
generation of palladacycles.[8g] Continuing in this concept, we explored oxime & other
N, O compound themes for ligands in the Mizoroki–Heck and Suzuki–Miyaura cou-
pling. While a vast number of N, O compounds are indeed readily available, some are

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3
Scheme 1. Oxime ligand–Pd catalysis of the Mizoroki–Heck reaction.
also easily synthesizable using well-known reactions in high yields. Here, we experi-
mented on the use of oximes and tertiary amines as well as ketones as ligands.
Results and discussion
In preliminary studies, we used DMG, which is commercially available, as the ligand
with Pd(OAc)2, to give high yields of the Mizoroki–Heck reaction product in short
reaction times[2] (Scheme 1). While palladacycles have been derived from the aromatic
oximes, we were curious about the catalytic activity of simple coordinating monodentate
and bidentate oximes which would not undergo cyclopalladation. Several ketones and
aldehydes are readily available for the derivatization of mono dentate oximes. We also
prepared a bidentate amino oxime from the Mannich base of acetophenone. High yields
are reported in the ligand free Pd(OAc)2 catalysis of the Mizoroki–Heck reaction of aryl
halides, though requiring long (19–44 h) reaction times (Fig. 1).[9]
The results of the Mizoroki–Heck reaction is shown in Table 1. Very high yields of
the E-substituted product were readily obtained from the different aryl iodides and
Pd(OAc)2 as catalyst under standard Mizoroki–Heck reaction conditions. Though the
reactions were carried out under argon, the reactions could be performed under ambi-
ent conditions in presence of air, without much depletion of the reaction or the yield.
NMP and K2CO3 were the solvent and base of choice for the reaction.
Monodentate oximes gave high yields of the reaction substitution product as
expected. We had anticipated some steric acceleration from hindered ketone oximes but
surprisingly camphor oxime gave reduced yield. The chelating oximes also gave high
yields. Similarly, the dimethyl amine group was easily incorporated by the Mannich
reaction of acetophenone and the derived chelating oxime, gave excellent yields of the
Mizoroki–Heck product.
The reaction of 1,2-disubstituted alkene was also tested with the acetophenone oxime
ligand. We have reported silver sequestration of aryl halides for high yielding
Mizoroki–Heck reaction of 1,1-and 1,2-disubstituted alkenes.[10] Cinnamaldehyde
reacted with 4-iodoanisole catalyzed by Pd(OAc)2 and acetophenone oxime ligand
under standard conditions (with addition of 1 Eq TBABr, Scheme 2, Table 2, footnote),
to provide the product in 99% isolated yield. TBABr is essential for good yields acting
as solid–liquid phase transfer agent.[11] Preliminary experiments report the reaction to
be successful with other 1, 2-disubstituted alkenes like ethyl cinnamate and stilbene.
Iodobenzene reacted with stilbene providing product in 41% yield (Scheme 2). DMF
was used as solvent for all the reactions while the base was NaOAc or K2CO3. With 4-
iodoanisole the E:Z ratios were low, between 2: 1 and 3: 1 (Table 2).

4
P. G. BANGAR ET AL.
O
HOH
O
N-OH
N-OH
N-OH
HO
HO
H
N-OH
O
H
H
OH
HO
H
L-1 Cyclohexanone oxime
L-3 Benzil
L-4 Acetophenone Oxime
L-5 Camphor
L-6 Tetralone Oxime
L-2 D-Glucose
O
HO
OH
N
N
HO
N
OH
Me
Me
NMe
2
OH
S
N
N-OH
N
N-OH
OH
L-10 Thiophene-2-
carbaldehyde oxime
L-8 (E)-3-(Dimethylamino)-1-
phenylpropan-1-one oxime
L-11 Dimethyl
glyoxime
L-7 Pyridine-2-carbaldehyde
oxime
L-12 Benzoin
L-9 Benzoin- -oxime
Figure 1. Structures of various oxime & N, O – ligands.
Table 1. Oxime ligands in Pd catalysts of the Mizoroki–Heck reaction.
S. no.
Aryl iodide
Alkene
Ligand
Time (h) Yield (%)
1
2
3
4
5
6
7
8
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
C6H5I
Ethyl acrylate CyOxime – L1
Ethyl acrylate D-Glucose – L2
Ethyl acrylate CyOxime – L1
Ethyl acrylate Benzil – L3
Ethyl acrylate Acetophenone oxime – L4
Styrene Acetophenone oxime – L4
Ethyl acrylate Camphor oxime – L5
5
7
4
4
5
96
85
100
94
63
79
65
82
65
90
87
77
65
91
84
88
94
78
80
97
92
5
15
19
19
22
22
24
24
24
22
24
24
24
3
Styrene
Styrene
Tetralone oxime – L6
Pyridine-2-carbaldehyde oxime – L7
9
10
11
12
13
14
15
16
17
18
19
20
21
Ethyl acrylate (E)-3-(Dimethylamino)-1-phenylpropan-1-one oxime – L8
Ethyl acrylate Benzoin-a-oxime – L9
Ethyl acrylate Tetralone oxime – L6
Ethyl acrylate Pyridine-2-carbaldehyde oxime – L7
Ethyl acrylate Thiophene-2-carbaldehyde oxime – L10
4-CH3OꢀC6H4I Ethyl acrylate (E)-3-(Dimethylamino)-1-phenylpropan-1-one oxime – L8
4-CH3OꢀC6H4I Ethyl acrylate Tetralone oxime – L6
4-CH3OꢀC6H4I Ethyl acrylate Thiophene-2-carbaldehyde oxime – L10
4-CH3OꢀC6H4I Ethyl acrylate Pyridine-2-carbaldehyde oxime – L7
4-CH3OꢀC6H4I Styrene
DMG – L11
Ethyl acrylate DMG – L11
Ethyl acrylate DMG – L11
4-CH3ꢀC6H4I
4-FꢀC6H4I
2
3
Scheme 2. Mizoroki–Heck reaction of 1,2-disubstituted alkenes.
Table 2. Acetophenone oxime as ligand for the Mizoroki–Heck reaction of 1,2-disubstituted alkenes.
S. no.
Aryl iodide
Alkene
Base
Time (h)
Yield (%)
E:Z ratioa
1
2
3
4
4-CH3OꢀC6H5I
Ethyl cinnamate (E)
Cinnamaldehyde (E)
Stilbene (E)
NaOAc
NaOAc
K2CO3
K2CO3
40
24
44
48
64
99
41
49
(3:1)
–
–
(2:1)
C6H5I
C6H5I
4-CH3OꢀC6H5I
Stilbene (E)
Reaction conditions: Aryl iodide (1.5 mmol), alkene (1 mmol), Pd(OAc)2 (2 mol%), acetophenone oxime (4–5 mol%),
NaOAc (1.5 mmol), TBABr (1 mmol), 10 ml DMF, temp: 100 ꢁC then increased to 130 ꢁC after 7 h.
aE:Z ratio was determined by 1H NMR.

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5
Pd(OAc)2 0.5 - 3 mol %
0.5 - 3 mol %
B(OH)2
I
L
R'
+
K3PO4 1.2 - 2 mmol
TBABr, NMP, 100 oC
R'
R
R
47 - 92 % Yield
R : H, 4-Cl, 4-CH3O, 4-CH3, 1-Nap
R' : H, 4-CH3, 1-Nap, 4-Cl
Scheme 3. Oxime ligands–Pd(OAc)2 catalyzed Suzuki coupling.
Table 3. Oxime & other ligands in Pd catalysis of the Suzuki coupling.
S. no.
Aryl iodide
Boronic acid
Ligand
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
9
4-ClꢀC6H4I
C6H5B(OH)2
C6H5B(OH)2
C6H5B(OH)2
4-CH3C6H5B(OH)2
4-Cl.C6H5B(OH)2
1-Nap.B(OH)2
C6H5B(OH)2
C6H5B(OH)2
C6H5B(OH)2
CyOxime – L1
Benzil – L3
Benzoin – L12
Benzoin – L12
DMG – L11
DMG – L11
DMG – L11
CyOxime – L1
Acetophenone oxime – L4
24
10
10
14
2.15
1
2
92a
69a
47a
60a
83b
89b
88b
75b
79b
C6H5I
C6H5I
4-ClꢀC6H5I
C6H5I
4-CH3OꢀC6H5I
4-CH3OꢀC6H5I
4-CH3ꢀC6H5I
1-NapꢀBr
30 min
1.30
Reactions conditions: ArI (0.5 mmol), ArB(OH)2 (0.6 mmol), K3PO4 (0.6 mmol), TBABr (0.6 mmol), Pd(OAc)2 (0.5–3 mol%),
ligand (0.5–3 mol%).
aNMP: 100 ꢁC, time: 10–24 h.
bDioxane:water (1:1), 100 ꢁC, time: 30 min–2.5 h.
Pd(OAc)2 5 mol %
Acetophenone Oxime 5 mol %
K2CO3 5 mmol
I
+
n-Bu4NCl 1 mmol
DMF, 100 oC, 24 h
N
H
NH2
1 mmol
5 mmol
Scheme 4. The LaRock indole annulation.
88 % Yield
We also tested these oxime ligands for the catalysis of the Suzuki coupling by
Pd(OAc)2. Under unoptimized conditions, good yields of the various biaryls were
obtained (Scheme 3, Table 3).
Suzuki couplings of aryl halides have been reported to be high yielding in aque-
ous solvents.[8] The use of oxime ether ligands for Suzuki coupling with Pd catalysis
is reported where the in situ generation of Pd cycles is proposed to be the real cata-
lyst.[8g] Compared to this our study discusses the effect of oxime ligands for both
the Mizoroki–Heck reaction and Suzuki coupling and related annulations. Some of
the oximes we have studied do not form Pd cycles as evidenced by the activity of
cyclohexanone oxime as ligand. Our experiments for the Suzuki coupling in 1:1
dioxane water mixture gave excellent results. The reactions with different aryl iodides
and boronic acids using TBABr as additive were complete in 30 min to 2.5 h.
Cyclohexanone oxime and DMG were representative oxime ligands and gave very
high yields. Comparative studies were carried out with benzil, benzoin as ligands,
which gave relatively lower yields. 1-Bromo naphthalene gave the Suzuki coupling in
high yields. But, the reaction of 4-bromo anisole with phenyl boronic acid, both in

6
P. G. BANGAR ET AL.
Scheme 5. The isocoumarin annulation.
the presence or absence of TBABr gave multiple products, due to homo coupling
and cross-coupling.
The LaRock indole annulation was carried out with acetophenone oxime as ligand[12]
(Scheme 4). The reaction of 2-iodoaniline with 3-octyne gave the indole in 88% yield.
Similarly, 2-iodobenzoic acid reacted with 1-octyne to give the isocoumarin in 70%
yield[13] (Scheme 5).
Conclusion
Oximes are excellent ligands for the Pd catalyzed Mizoroki–Heck reaction and
Suzuki coupling. The oxime ligands can be readily derived from a vast library of
aldehydes and ketones. The less reactive 1,2-disubstituted alkenes also provided high
yields of trisubstituted products. The LaRock indole annulation and synthesis of iso-
coumarin could be carried out in very high yields in the presence of the acetophe-
none oxime ligand.
Experimental procedures
General procedure for the Mizoroki–Heck reaction
To an oven-dried 25 ml round bottom flask equipped with magnetic stirrer bar was
charged palladium acetate (1.5–4 mol%) and ligand (3–8 mol%) in NMP (1 ml). The
reaction mixture was stirred for 3 min. To this reaction mixture base K2CO3 (2 mmol),
aryl iodide (1 mmol), olefin (1–2.5 mmol), and NMP (3 ml) were added and the reaction
mixture was stirred at the indicated temperature for the indicated amount of time. At
the conclusion of the reaction as monitored by TLC, the crude reaction mixture was
quenched with water and extracted with ethyl acetate. The organic layer was washed
with brine, dried over Na2SO4, and concentrated under vacuum. The residue was puri-
fied by column chromatography on silica gel to give the desired product.
A1 2-Propenoic acid-3-phenyl, ethyl ester (2E) (4 h) (2 h, 0.126 g, 0.72 mmol, 72% yield,
1
colorless oil) CAS Registry Number 103-36-6, H NMR (CHLOROFORM-d, 200 MHz):
d (ppm) 7.65–7.73 (d, J ¼ 16 Hz, 1H), 7.32–7.57 (m, 5H), 6.40–6.48 (d, J ¼ 16 Hz, 1H),
4.14–4.38 (q, J ¼ 7.2 Hz, 2H), 1.20–1.44 (t, J ¼ 7.1 Hz, 3H) 13C NMR (CDCl3, d,
200 MHz): d 166.9, 144.48, 134.36, 130.13, 126.76, 127.96, 118.18, 60.40, 14.24; IR
(cmꢂ1) 3399, 3021, 2976, 2404, 1706, 1636, 1482, 1453, 1372, 1315, 1272, 1214, 1176,
1089, 1036, 984, 829, 871, 765, 675; HRMS-ESI: [MþþH]þ calcd for C11H12O2
[M þ H]þ 177.0910, found: 177.0912.

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7
General procedure for the catalysis of Suzuki coupling
To a solution of aryl halide (0.078 g, 0.5 mmol), aryl boronic acid (0.073 g, 0.6 mmol),
TBABr (0.161 g, 0.5 mmol), and K3PO4 (0.127 g, 0.6 mmol) in dioxane and water (1:1,
10 ml) was added Pd(OAc)2 (0.0022 g, 0.01 mmol) and ligand (0.01 mmol). The resulting
mixture was heated with stirring at 130 ꢁC for 2–6 h under argon. After completion of
reaction (monitored by TLC), the reaction mixture was quenched by adding water. The
solution was extracted with ethyl acetate (3 ꢃ 20 ml) the combined extract was washed
with saturated brine and dried over anhydrous Na2SO4. The organic layer was concen-
trated under vacuum and the crude product purified by column chromatography on sil-
ica gel (100–200 mesh, petroleum ether: 2% ethyl acetate) to give pure product.
B1 1,1-Biphenyl-4-chloro (5i) (2 h, 0.089 g, 0.94 mmol, 95% yield, white solid, MP:
1
79 ꢁC) CAS Registry Number 2051-62-9, H NMR (200 MHz, CDCl3, d): 7.60 ꢂ 7.37
(m, 9 H); 13C NMR (200 MHz, CDCl3, d): 139.98, 139.65, 133.35, 128.88, 128.37,
126.97; IR (cmꢂ1): 3022, 2923, 2403, 1894, 1755, 1657, 1597, 1480, 1398, 1218, 1091,
1012, 924, 834, 768, 677; HRMS-ESI: [M]þ calcd for C12H9Cl [M]þ 188.0387,
found: 188.0386.
Procedure for LaRock indole annulation using acetophenone oxime ligand – Palladium
acetate (0.011 g, 5 mol%), acetophenone oxime (0.007 g, 5 mol%), n-Bu4NCl (0.277 g,
1 mmol), K2CO3 (0.691 g, 5 mmol), 2-iodoaniline (0.219 g, 1 mmol), 4-octyne (0.551 g,
5 mmol), and DMF (10 ml) were added to an oven-dried 25 ml round bottom flask
equipped with magnetic stirrer bar. The system was degassed and heated at 100 ꢁC for
24 h. At the conclusion of the reaction as monitored by TLC, the reaction mixture was
diluted with ethyl acetate and washed with saturated aqueous ammonium chloride and
water. The organic layer was dried over anhydrous Na2SO4, filtered, and concentrated.
The product was purified by column chromatography on silica gel to give analytically
pure product (0.177 g, 88%).
1
2,3-Dipropyl-1H-indole – H NMR (CDCl3, 200 MHz) d ¼ 7.71 (s, 1H), 7.54–7.50 (m,
1H), 7.30–7.26 (m, 1H), 7.14–7.02 (m, 2H), 2.74–2.63 (m, 4H), 1.78–1.57 (m, 4H), 0.97
(q, J ¼ 7.33 Hz, 6H); 13C NMR (CDCl3, 50 MHz) d ¼ 135.23, 135.14, 128.79, 120.73,
118.81, 118.35, 112.10, 110.14, 29.68, 28.12, 26.23, 24.09, 23.14, 14.23, 13.97; IR (CHCl3)
ꢀmax¼3412, 2961, 2931, 1608, 1575, 1462, 1352, 903, 752, 735; HRMS: m/z¼calcd for
C14H19N [M]þ 201.1517, found: 201.1513.
Procedure for isocoumarin synthesis using acetophenone oxime ligand – To a solution
consisting of 2-iodobenzoic acid (0.248 g, 1 mmol), 1-octyne (0.330 g, 3 mmol), and
Et3N (0.69 ml, 5 mmol) in DMF (1 ml) under argon were added Pd(OAc)2 (0.011 g,
5 mol%), acetophenone oxime (0.014 g, 10 mol%), and zinc chloride (0.136 g, 1 mmol).
The mixture was heated at 100 ꢁC for 24 h. At the conclusion of the reaction as moni-
tored by TLC, the reaction mixture was diluted with ethyl acetate and washed with satu-
rated aqueous ammonium chloride and water. The organic layer was dried over
anhydrous Na2SO4, filtered, and concentrated. The product was purified by column
chromatography on silica gel to give analytically pure product (0.161 g, 70%).
1
3-Hexyl-1H-isochromen-1-one – H NMR (CDCl3, 200 MHz) d ¼ 8.25 (d, J ¼ 7.96 Hz,
1H), 7.71–7.63 (m, 1H), 7.48–7.33 (m, 2H), 6.26 (s, 1H), 2.52 (t, J ¼ 7.71 Hz, 2H),
1.78–1.63 (m, 2H), 1.44–1.26 (m, 6H), 0.92–0.86 (m, 3H); 13C NMR (CDCl3, 50 MHz)
d ¼ 163.07, 158.29, 137.60, 134.64, 129.43, 127.46, 124.96, 120.06, 102.81, 33.48, 31.45,

8
P. G. BANGAR ET AL.
28.63, 26.81, 22.46, 13.99; IR (CHCl3) ꢀmax¼3066, 2932, 2860, 1806, 1732, 1656, 1473,
1318, 1213, 1155, 1028, 826, 754, 688; HRMS: m/z¼calcd for C15H18NaO2 [M þ Na]þ
253.1199; found: 253.1204.
Funding
CSIR is acknowledged for scholarships, SRF to PGB and Dr. H. V. Thulasiram for CSC NAPA
PA-II to Pradip Nahide.
ORCID
Suresh Iyer
http://orcid.org/0000-0003-3293-2075
References
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